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WILLIAM KEMBLE HALL, OF WEST HOBOKEN, NEWJERSEY.

SAFETY APPARATUS FOR STEAM-BOILERS.

Specification lof Letters Patent No. 19,568, dated March 9, 1858.

To all whom 'it may concern:

Be it known that 'I, WILLIAM KE-MBLE HALL, of West-Hoboken, in the county of Hudson and State of New Jersey, at present residing in London, England, have invented a new and useful Apparatus for Preventing the Bursting of Steam-Boilers; and I do hereby declare that the following is a full and exact description thereof.

All the cont-rivances hitherto adopted for the purpose of providing against explosions are designed to supply water when that in the boiler has fallen to too low a level, or to open the safety valve by the pressure of steam irrespective of other circumstances. As has been illustrated by many published examples of either of these plans would induce in many 'instances the very accident it was designed to avoid, and there seems every reason to believe a large majority of explosions are occasioned, not by a pressure of steam allowed steadily to increase until its tension is greater than the strength of the boiler, but by the negligence of the attendant in permitting the level of the water to fall 'below the flues, exposing the plates to a high temperature and surcharging. the steam with caloric far exceeding that due to its pressure. In injecting an additional supply of water into the boiler when in this dangerous condition, it is thrown over the heated plates and into the super-heated steam and suddenly converted into steam of perhaps too high a tension for the boiler; and so instantaneously moreover that it operates with all the momentum of a blow, and as the Water necessary to produce this disastrous result may be supplied from that already in the boiler by the agitation incident to the escape of steam from the opening of the, so-called, safety valve, the alarming fact is presented that the very instrument now provided for insuring against explosions may become the cause of producing one. These considerations naturally and inevitably lead to the conclusion that safety is only to be attained by opening a water blow-oft' valve when the surface of the water Ahas fallen to a perilous extent, for the purpose of first discharging t-he water which is the more dangerous agent, and then the steamoperating in fact as a water safety valve placed in a more useful and less objectionable position than the present steam valve placed on the dome.

By thus depriving the boiler of water it mightv be injured and perhaps the lues destroyed by the fire, but it could not be exploded. 1

The nature of my invention consists in providing a steam boiler with a valve communicating with the water and retained in its seat and kept. closed by a rod soldered at one or more points to the heat-ing surface of the boiler, in such a manner that when by negligence or otherwise, the surface of the water has fallen to a dangerous extent and allowed the boiler to become overheated, the valve is released by the melting of the solder or fusible metal employed to detain the rod, and opened bythe pressure of the steam, and the water and steam blown from the boiler.

To enable others skilled in the art to make and use my invention, I will proceed to describe its construction and operation, reference being had to the accompanying drawing and to the letters of reference markedV thereon.

The same letters in the various figures re fer to similar parts.

Figure 1, is al section of an ordinary cylindrical boiler with a single internal flue, fittedvwith this apparatus. Fig. 2 is a side elevation of the apparatus as applied in the preceding figure.

a is a valve communicating with the water in the boiler by a pipe ZJ.

c, CZ, e, is a rod serving as a stem to the valve a, made in two parts jointed at d, for convenience of construction, and terminating at its lower end e, with a button or flange. The upper end o, of this rod or valve stem is cut with a screw thread and furnished with a nut by which the valve may be secured tightly in its seat.

f, is a cup, bolted or otherwise fastened to the upper portion of the flue, into which the valve stem o, d, c, is secured with tin or any other readily fusible metal, alloy or compound. vWhen the tin in the cup f, is melted, the valve a is opened by the pressure of the steam and the water and the steam discharged from the boiler through the pipe ZJ. The cup f, should be made of copper or other good conductor of heat and should be placed in the position first exposed tothe action of the heat by the falling of the surface of the water, or in any other position, where, by malformation of the boiler or otherwise the plates are most likely to become nprotected by water from the action of the g, is a Washer of vulcanized india rubber placed under the nut on the valve stem by Which the valve is secured to its seat, for the purpose of compensating by its elasticity for any difference in the expansion of the boiler and its flue and the valve stem.

7L, is a pipe by which the Water and steam when discharged from the boiler may be employed to extinguish the fire or conducted to any suitable place. The pipe 71, may also be used as the inside feed pipe from the force pump.

Fig. 3 represents the application of my invention to a boiler with external flues. Fig. 4 shows its arrangement when applied to a boiler with two 4internal flues. Figs. 5 and 6 show a form of the cup for holding the fusible metal with Which-the valve rod is secured differing from that shown at v7c in Figs. l and 2. Fig. 7 is a modification of the joint Z in the valve rod c a7, e by which the inequality of expansion may be compensated by the elasticity of the joint pin independent of the ring of india rubber represented at g in Fig. 1. The same purpose may be accomplished by an ordinary helical spring.

I am aware that Cadwallader Evans in April 1839 invented an arrangement by Which the melting of a plug allowed the steam to escape and caused a Weight to fall and open a cock by Which Water from a reservoir might eXtinguish'the fire; that John l?. Balrewell in December 1839 patented an apparatus by which the steam only was blown from the boiler on the melting of a plug; and that in May 1855 A. M. Glover proposed an apparatus by Which an over pressure of steam when the boiler had a full supply of Water would force some of the Water into the furnace, and When the Water became lo7 in such a case would permit the escape of steam; thus occasioning in various Ways the premature escape of steam Which my apparatus is designed to prevent, and which in many instances seems to have been the final link in the chain of circumstances leading to t-he apprehended disaster. But

Vhat I do claim as my invention and desire to secure by Letters Patent is The combination of a valve, fusible metal, and intervening elastic substance, and a pipe leading from the loWer part of the boiler, as described, by Which the Water may first be discharged from a boiler when dangerously overheated, and employed if desired to eX- tinguish the fire.

WILLIAM KEMBLE HALL.

Witnesses JOHN Gr. BRETT, CHAs. JOSEPH. 

